Scaly rhizome formation in Achimenes cv. Primadonna was investigated under controlled conditions in growth chambers. When plants from seeds were grown at 30-25°C (day/night), scaly rhizome formation was delayed. Plants from cuttings grown at 30-25°C showed a delay in scaly rhizome formation. Also, in plants grown from rhizomes, the number of scaly rhizomes and fresh weight of scaly rhizome were lowest at 30-25°C. These results indicate that high temperature at 30-25°C retards the scaly rhizome formation in Achimenes. INTRODUCTION The genus Achimenes belongs to the Gesneriaceae. About 25 species are native to Mexico, Brazil, northern Argentina and Jamaica. Achimenes are herbaceous plants having rhizomes that develop at the base of the shoots and on underground stolons at the end of the growing season. Deutch (1974) reported that bulblet (= scaly rhizome) formation in Achimenes cuttings was inhibited by long-day treatment such as continuous illumination. However, in other reports, rhizome formation was not significantly affected by daylength or by growing temperature of 17, 21 or 25°C (Vlahos, 1990a, b). It is uncertain whether higher temperatures affect rhizome formation. Scaly rhizome formation of Achimenes was investigated at various growing temperatures in plants raised from seeds, cuttings or scaly rhizomes.